Hi, Thank you for your query. I can understand your concerns. No treatment is usually required for pityriasis rosea. Oral antihistamines or topical steroids may be used to decrease itching. Calamine lotion may be soothing to the skin and reduce itching and has no side-effects. Irritants such as soaps with fragrances, hot water, wool, and synthetic fabrics should be avoided. Direct sunlight makes the lesions resolve more quickly. UV therapy is most beneficial in the first week of the eruption. Muscle weakness & asthenia can occur with antihistamines. Stop Zyrtec (cetirizine) ,an antihistamine. If your tiredness still persist ,go for further evaluation. Regards Dr. T.K. Biswas M.D. Mumbai